William Ross Casement was a passenger in the car which knocked down the student

Student Enda Dolan was killed as he walked back to Queen’s Elms village

Enda Dolan with his girlfriend Sarah Graham before their school formal

Enda on the couch with all of his younger siblings

A portrait of the family together

Enda Dolan playing the guitar on stage at his old school

This is the face of killer driver David Lee Stewart who was given just three-and-half years in jail for mowing down 18-year-old student Enda Dolan

Last month, Stewart (31), of Gray's Park Avenue, Belfast, pleaded guilty to causing Enda's death by dangerous driving, as well as four other motoring offences, including dangerous driving and failing to provide a specimen of blood.

"Enda’s death was the catastrophic result of someone who decided to drink and drive.

"There is absolutely no excuse for drinking and driving and there is no such thing as a safe amount. It ruins lives. Not just those of the people who are killed, injured or left to deal with the consequences, but also for those responsible."

Prosecutors have been urged to appeal the sentence given to Stewart.

A decision on whether to refer the matter to the Court of Appeal will now be taken by Barra McGrory, Northern Ireland's chief prosecutor.

The Dolan family said they were "disappointed and disgusted" at the sentences.

Yesterday, the Public Prosecution Service (PPS) confirmed it had been asked to investigate.

A PPS spokesperson said: "The PPS can confirm that we have received correspondence outlining concerns over the sentences passed in this case.

"The matters raised will be examined carefully in line with our protocols around unduly lenient sentences in the Crown Court."

It is understood that the request did not come from the Dolan family.

Enda, from Killyclogher in Co Tyrone, was an architecture student at Queen's University.

He had been walking to his student accommodation at Elms Village when a van driven by Stewart mounted a footpath and hit him. Stewart drove on for 800 metres with the teenager on the roof of his vehicle.

Stewart admitted a series of charges linked to the teenager's death, including causing death by dangerous driving.

He will spend three-and-a-half years in prison and the same amount of time on licence. He was also banned from driving for five years.

"We have been left with a life sentence," Mr Dolan added. "So many parents have stood in our shoes... and many more will in the future unless something is done to deter individuals from driving under the influence of drink and drugs."

Road safety campaigners also voiced their anger at the sentences. Gary Rae from the charity Brake said: "We share the disgust of Enda's family at the paltry length of this sentence.

"We must see tougher sentences to fully fit the crime to give families justice and also act as a proper deterrent."